| A static route or address through the Domain Name System (DNS) can be established to resolve an IP address. Such a Static Route would not change even if a new IP address is assigned while a dynamic one would incur an additional cost. The dynamic one will allocate a new IP address during startup, during a shutdown, or as part of a restart process. If you have ever been surfing the Internet, you have probably come across pages that had some sort of advertisement before being displayed pages in a standard web browser. It is not only ads that require service name resolution, and page display time synchronization. Even when operating systems are on the same machine, such as Linux, there are differences between the various kernels. kernel is what controls the services and how they are executed. Each service has a different set of commands that control it. As you know from your service word processing experience, the command line is where you get information about the services, and how they work. The domain name system first discovered and implemented by routers in the early 90's with the passage of the ARPANET, and it is still used today. ARPANET itself no longer exists, and most people are familiar with it only by hearing about ARPANET in conjunction with the Internet. In its place is the new internetworking system of the IETF, which stands for Internet Research Base Protocol for Applications. For those that are unfamiliar with the workings of the DNS, a brief explanation will be beneficial. There are essentially three parts to a DNS, or Domain Name System. First there is the root server, which is the first point in the system where all other namespaces are registered. Every name in the hierarchy must be delegated a certain numeric IP address to distinguish them from each other. Next there is the zone which is reserved for the specific IP address. The last level of namespces within the DNS is reserved for the names of DNS servers that have been registered with that host name. As you can see, DNS is broken down into three separate but intimately connected parts. All of these parts, or parts if you will, play an important role in the functionality of the domain system as a whole. The next thing we will look at is the so called ISP, or Internet Service Provider. This is basically the company that everyone uses to connect to the domain system, either by DSL, cable, or even wireless connections. Now you might be wondering why it is important to have a domain name? In essence the simple fact is that it secures your privacy, as well as the security of your data. The DNS can only secure your domain names and IP addresses when you have connectivity to the internet. This means that any time you are not connected to the internet you are opening up an attack vector which can be very dangerous and also very serious because anyone can connect to your domain name and change what you are trying to say. You can prevent this attack by securing your domain names before you register a domain name. When you register a domain name for your company you will be given your business domain name and an IP address. These IP addresses and domain names can be available to anyone. As a matter of fact, anybody can create a fake email account under your business name and try to trick you into revealing your sensitive information. This can be very dangerous because any time the company that owns the domain is looking for information, the information that they are looking for is the IP address of the domain. And any time you have an email account, and someone starts sending you sensitive information such as your bank account number, credit card number or social security number it can be compromised. To protect yourself when you need to protect yourself when you are working with the startup configuration of your network device, the best way to do it is to set up a firewall between all the interfaces. One of the most common ways to configure a firewall is to use the iptables chkconfig utility, which you can access with the command shell prompt by typing "kshc" or "ksh" followed by a colon. The good thing about using the iptables chkconfig utility is that you can make this setting only be used for certain interfaces or for all interfaces, so when you are not in the command shell the iptables chkconfig will not affect your startup configuration. |